Generally, the structure of a liquid crystal color display comprises a first multilayer construction having provided on a transparent substrate such as a glass plate and laminated in the following order, a color filter, a protective film, a clear electrode having a matrix-form pattern, an insulating film and an orientation film, and a second multilayer construction provided on a transparent substrate such as a glass plate and laminated in the following order, a sheet-form or striped-pattern of clear electrode and an orientation film, said multilayer structures being opposed such that their respective orientation films face each other to form an inner cell having a thickness defined by a spacer, which cell contains a liquid crystal material. The composite structure is arranged between two polarizing plates. Alternatively, in the first multilayer construction, the clear electrode having a matrix-form pattern may be positioned between the color filter and the transparent substrate.
The color filter generally comprises red, blue and green dot-form images each arranged in a matrix pattern, and their respective boundaries are partitioned by a black matrix.
Also, automobile meters and tachometer panels a generally employ a plastic substrate provided with images of various colors including yellow, cyan, magenta and black colors.
For the purpose of forming colored images on a support as in the above noted applications, a wide variety of methods have hitherto been proposed.
For example, the preparation of a color filter for a liquid crystal display is discussed below.
First, a multicolor image is formed on a transparent substrate, such as a glass plate, used as a support in accordance with (1) a dyeing method, (2) a printing method, or (3) a method using light-sensitive colored resin solutions (i.e., a colored resist method) as disclosed in JP-A-63-298304 (The term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-63-309916, JP-A-01-152449, etc., wherein a light-sensitive colored resin solution is coated, exposed and developed in succession, and these steps are then repeated. Also, a multicolor image can be formed using (4) a method which comprises transferring successively colored images formed on their respective temporary supports onto a final support or another temporary support, as disclosed in JP-A-61-99103, JP-A-61-233704 or JP- A-61-279802, (5) a method as disclosed in JP-A-61-99102, wherein a previously colored light-sensitive resin solution is coated on a temporary support to form a colored layer, the colored layer is transferred directly onto a transparent substrate and then subjected successively to exposure and development, and these steps are then repeated, or (6) a method as disclosed in JP-A-61-256303, which comprises forming a multicolor image on a temporary support by repetition of steps consisting of transfer of a light-sensitive colored layer onto a temporary support, exposure and development, and transferring the thus formed multicolor image onto a final support such as a glass plate. In addition, an electrodeposition method, a photographic method, an evaporation method, a decolorization method, etc., have been used for the above-described purpose.
A protective layer is then formed on the polychromatic colored image for the purpose of physically and chemically protecting the colored image and for leveling the image surface. The protective layer generally comprises a film of high transparency, e.g., a resin film of acryl, urethane, silicone or like type, or a film of metal oxide such as silicon oxide, that is formed using a spin coating process, a roll coating process, a printing process, etc. If necessary, the structure is subjected to level standing and solvent removal, followed by a cure processing.
On the protective layer, a transparent conductive film, such as a tin indium oxide (ITO) film or a tin oxide film, is further formed using a vacuum film-forming process, such as a sputtering process, a vacuum deposition process or the like. An electrode pattern is then formed using a mask evaporation method, an etching method etc., to form a clear patterned electrode layer. The clear patterned layer may also be formed on the transparent substrate below the colored image and the black matrix layer.
Each of the above described conventional methods for forming colored images in the preparation of a color filter are disadvantageous for various reasons as discussed below.
In the dyeing method (1), the steps of coating a photoresist and partly dyeing the dried transparent film are repeated. Thus, repetition of the formation and removal of a reserve printing layer is required such that the production process is complex.
In the printing method (2), the printing ink is poorly transferable to glass such that the colored patterns tend to be inferior in shape and uneven in density. Also, registering is required to prepare three or four differently colored patterns. Therefore, it is difficult to form a color filter of high quality using this method.
In the method (3), the density of the colored layer varies with the thickness of the layer, such that an accurate coating technique is required to provide uniform density throughout the colored layer. In addition, the second colored layer is difficult to coat uniformly since the first colored layer formed prior to coating of the second colored layer has an uneven surface.
In the method (4), it is difficult to precisely arrange images of different colors at their individually intended positions (hereinafter, "registering") upon multiple separate transfers of the colored images to the final support.
As for the methods (5) and (6), although the process for forming colored images is simplified, and although it is easy to control exposure, development and density, and although the registering is also performed without difficulty, these methods are still disadvantageous for reasons as follows.
JP-A-61-99102, JP-A-61-256303 and JP-A-63-187203 disclose methods of producing a color filter, which comprise providing light-sensitive colored resin layers on the surface of a transparent substrate using a transfer technique, and transferring to the final support which is substantially transparent. Transferrable red, blue and green images are formed one after another by imagewise exposure and development. According to these methods, no deviation is caused in the transfer step with respect to the registering of differently colored images. Therefore, these methods are attractive. Moreover, since the light-sensitive colored resin layers previously coated in a uniform and definite thickness are transferred, exposure and development characteristics are stabilized, and good density control of colored images is realized.
However, the colored image that is first formed on the adhesive layer has a height of several microns in accordance with these methods, such that sufficient interlayer contact cannot be realized upon the subsequent transfer of additional colored light-sensitive resin layers. Consequently, colored images formed through exposure and subsequent development steps after the formation of the first colored image are not in sufficient contact with one another.